How do they work out the gaps between two riders on the road? I guess you need their exact position (a GPS will tell you that), the distance between them along the race route (not as the crow flies) and their exact speed (a GPS will tell you that too). Subtract the slower speed from the faster one, then calculate how long it takes you to cover that distance at that speed. Repeat lots of times a second, and I guess that’s how it’s done – at least, when one is converging on the other. When the rider in front is pulling away from the one behind, I can’t immediately imagine how they do it, so, since I need to publish this tonight, let’s leave it at that.